Method of detecting a leak in a hydraulic pitch system

Abstract

Provided is a method of detecting a leak in a hydraulic cylinder of a rotor blade pitch system of a wind turbine including a plurality of rotor blades, which method includes the steps of selecting one of the pitch systems to undergo a functionality test; actuating a fluid pump to move the pistons of the hydraulic cylinders of the pitch systems to their outermost positions; monitoring the hydraulic cylinder pressure levels of the non-selected pitch systems while performing the functionality test on the selected pitch system; and analyzing the monitored hydraulic cylinder pressure levels of the pitch systems to detect a drop in pressure in a pitch cylinder of a non-selected pitch system. A leak detection arrangement of a pitch-controlled wind turbine; and a pitch-controlled wind turbine are also provided.

The invention claimed is: 
     
       1. A method of detecting a leak in a hydraulic cylinder of a rotor blade pitch system of a wind turbine comprising a plurality of rotor blades, the method comprising:
 selecting a pitch system of the pitch systems to undergo a functionality test; 
 actuating a fluid pump to move pistons of the hydraulic cylinders of the pitch systems to an outermost position; 
 monitoring hydraulic cylinder pressure levels of non-selected pitch systems while performing the functionality test on the pitch system; and 
 analyzing the hydraulic cylinder pressure levels of the pitch systems to detect a drop in pressure in a pitch cylinder of a non-selected pitch system. 
 
     
     
       2. The method according to  claim 1 , wherein a cylinder pressure level is reported by a pressure sensor of a corresponding pitch system. 
     
     
       3. The method according to  claim 1 , wherein a pressure sensor is arranged in a fluid supply line connecting a pressurized fluid source to the pitch cylinders of the pitch system. 
     
     
       4. The method according to  claim 1 , further comprising reporting a cylinder fault when a drop in pressure is observed for the non-selected pitch system. 
     
     
       5. A pitch-controlled wind turbine comprising a plurality of rotor blades, wherein each rotor blade is turned by a dedicated pitch system, and wherein the dedicated pitch systems is part of a common hydraulic circuit, the pitch-controlled wind turbine comprising:
 a scheduler module configured to schedule a functionality test for a selected pitch system and to regulate a hydraulic circuit to move pistons of hydraulic cylinders of each pitch system; and 
 a leak detection arrangement to identify a faulty pitch system during a functionality test, the leak detection arrangement comprises an evaluation unit configured to receive:
 a first input signal identifying a selected pitch system scheduled for a functionality test; 
 a second input signal defining a duration of the functionality test; and 
 pressure level readings of the hydraulic cylinders of each pitch systems; 
 
 wherein the evaluation unit is further configured to track a temporal progression of a pressure reading and to identify a fault-indicative reduction in pressure. 
 
     
     
       6. The pitch-controlled wind turbine according to  claim 5 , wherein a fault-indicative reduction in pressure is indicated when a pressure reading of a non-selected pitch system decreases to less than 5% of an initial value during the functionality test. 
     
     
       7. The pitch-controlled wind turbine according to  claim 6 , comprising an error reporting unit configured to issue an error report to a wind turbine controller, the error report identifying the non-selected pitch system for which the fault-indicative reduction in pressure was observed during the functionality test. 
     
     
       8. The pitch-controlled wind turbine according to  claim 5 , wherein the scheduler module is configured to schedule a functionality test for a pitch system at intervals of at most 100-120 hours.